Large Eddy Simulation of Flow Structures in the Sydney Swirl Burner

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

Abstract

This thesis represents the research on swirling flow using large eddy simulation(LES). Three cases from the Sydney swirl burner database have been chosen as test cases; one medium swirl isothermal case N29S054, one high swirl isothermal case N16S159 and one medium swirl reacting case SM1.
The theories of LES and the corresponding closure models have been well
developed. This research focuses on statistical analysing flow field and characteristic features. Validation studies show good agreement in the isothermal cases, while for the reacting case, the LES predictions are less satisfactory.
There are two reverse flow zones presented in the medium isothermal case: the upstream one is induced by the bluff‐body, the downstream one is formed by bubble type vortex breakdown. The precessing vortex core is divided into several branches. In the high isothermal case, there is only one long recirculation zone which starts at the burner surface. As for the medium swirling isothermal case, there are two reverse flow zones in the reacting case. Due to the low stoichiometric mixture fraction in the methane flame, only the outer layer of the bluff‐body induced reverse zone is reactive. The main reactive zone is held at the bubblerecirculation.
By using two‐dimensional proper orthogonal decomposition (POD) on the cross‐plane, the periodic oscillating movement of the jet has been interpretation.
Through this research, a practical guideline is provided for the industry LES user.
Nevertheless, the LES method strategy has limitations concerning wall bounded
flows, especially for complex geometries typically found in industry. Multi‐phase
flows need special treatment.
Luk

Detaljer

This thesis represents the research on swirling flow using large eddy simulation(LES). Three cases from the Sydney swirl burner database have been chosen as test cases; one medium swirl isothermal case N29S054, one high swirl isothermal case N16S159 and one medium swirl reacting case SM1.
The theories of LES and the corresponding closure models have been well
developed. This research focuses on statistical analysing flow field and characteristic features. Validation studies show good agreement in the isothermal cases, while for the reacting case, the LES predictions are less satisfactory.
There are two reverse flow zones presented in the medium isothermal case: the upstream one is induced by the bluff‐body, the downstream one is formed by bubble type vortex breakdown. The precessing vortex core is divided into several branches. In the high isothermal case, there is only one long recirculation zone which starts at the burner surface. As for the medium swirling isothermal case, there are two reverse flow zones in the reacting case. Due to the low stoichiometric mixture fraction in the methane flame, only the outer layer of the bluff‐body induced reverse zone is reactive. The main reactive zone is held at the bubblerecirculation.
By using two‐dimensional proper orthogonal decomposition (POD) on the cross‐plane, the periodic oscillating movement of the jet has been interpretation.
Through this research, a practical guideline is provided for the industry LES user.
Nevertheless, the LES method strategy has limitations concerning wall bounded
flows, especially for complex geometries typically found in industry. Multi‐phase
flows need special treatment.
OriginalsprogEngelsk
ForlagDepartment of Energy Technology, Aalborg University
Antal sider174
StatusUdgivet - 2012
PublikationsartForskning
ID: 70020225